The passage from Dr. Louis Odier’s letter relative to an electric telegraph is given at A.D. 1773 (see J. J. Fahie, “A History of Electric Telegraphy to the Year 1837,” London, 1884, pp. 21–22).
A.D. 1600.—Gilbert—Gilberd—Gylberde (William), of Colchester (1544–1603), physician to Queen Elizabeth and to James I of England, justly called by Poggendorff “The Galileo of Magnetism,” publishes his “De magnete, Magneticisque Corporibus, et de Magno magnete tellure; Physiologia nova, plurimis et argumentis et experimentis demonstrata,” to which he had given “seventeen years of intense labour and research”[29] and which he dedicates “alone to the true philosophers, ingenuous minds, who not only in books but in things themselves look for knowledge,” and wherein the phenomena of electricity are first generalized and classified.
This great work is subdivided into six books, which respectively treat of the loadstone, of magnetic movements (coitio), of direction (directio), of variation (variatio), of declination (declinatio), and of the great magnet, the earth[30] of circular movement (revolutio).
Book I
After Gilbert has given in this Book an account of ancient and modern writings on the loadstone,[31] he indicates exactly what the latter is, where found, its different properties, and, having introduced us to his terrella-microge, or little earth[32]—a globular loadstone, showing that it has poles answering to the earth’s poles, he tells us all about iron ore, its natural and acquired poles, the medicinal virtues attributed by the ancients to iron as well as to the loadstone; and he ends this First Book with the announcement that loadstone and iron ore are the same, that iron is obtained from both, like other metals from their ores, and that all magnetic properties exist, though weaker, both in smelted iron and in iron ore; furthermore, that the terrestrial globe is magnetic and is a loadstone; and that just as in our hands the loadstone possesses all the primary powers (forces) of the earth, so the earth, by reason of the same potencies, lies ever in the same direction throughout the universe.
Book II
The justly famous Second Book contains Gilbert’s electrical work and, as is generally known, the second chapter thereof is the earliest ever published on electricity. We are here introduced to Gilbert’s versorium—a rotating needle electroscope[33]—and are given the results of his many experimental observations[34] and the opinions of others relative to magnetic coition or attraction. We find, throughout the whole of the second chapter, the first systematic study of amber, with an interesting list of electrics and the recognition of a group of anelectrics—non-electrics. After pointing out the different kinds of attractions admitted by Galen and other ancient writers, we are told that:
“Only feeble power of attraction is possessed by some electrics (all which have their own distinct effluvia) in favouring dry atmosphere: observable in midwinter while the atmosphere is very cold, clear and thin, when the electric effluvia of the earth offer less impediment and electric bodies are harder—that these bodies then draw, as well, all metals, wood, leaves, stones, earths, even water and oil, in short, whatever things appeal to our senses or are solid.
“All bodies are attracted by electrics, save those which are afire or flaming or extremely rarefied.
“Very many electric bodies do not attract at all, unless they are first rubbed. An ordinary piece of amber does not attract by heat, even when brought to the flaming point, but it attracts by friction, without which latter few bodies give out their true natural electric emanation and effluvium. By friction, the amber is made moderately hot and also smooth; these conditions must in most cases concur; but a large polished piece of amber or of jet attracts even without friction, though not so strongly; yet, if it be carefully brought nigh to a flame or a red coal, it does not attract corpuscles; further, the sun’s heat heightened by means of a burning-glass imparts no power to amber, for it dissipates and spoils all the electric effluvia. Again, flaming sulphur and burning sealing-wax (of lac) do not attract.